[Mailman-Users] mail loops: list-request and vacation messages

Chuq Von Rospach chuqui at plaidworks.com
Tue Jun 26 05:49:40 CEST 2001

On Monday, June 25, 2001, at 08:39 PM, Bob Puff at NLE wrote:

> Hmm, can't say I've seen the long turnaround, but you could still play 
> with the numbers, based on the fact that the mailbot will generate one 
> reply for every message it receives.

My worst case (and I swear this is true). I found a mail loop by pure 
accident that had been going on for over three months, between my 
majordomo software and someone's "I don't work here any more". Both 
sides were nice enough to append the entire previous message, of course. 
He'd send a message saying "I don't work here any more!", and majordomo 
would reply "I don't recognize that command!".

When I found it, the file being sent back and forth was 90 megabytes. It 
was making a round trip about every 18 hours. When it started, it was 
much smaller (it started out as about a 2K message, but every round 
trip, majordomo added 10K, and he added another 2K), and cycled about 
every two hours.

I found it because I was working on my sendmail installation, and I said 
to myself "self! why is there a 90 megabyte e-mail message in here?"

Of course, he stripped the subject and replaced it with his own. He 
stripped any identifying headers in the included body. He stripped the 
message ID and any reference to an existing one. he didn't include any 
key word to trap against. And he responded to everything.

Even if I wanted to trap that beast, there was no hook on it to trap, 
and it travelled slow enough (even at the beginning) that if I wanted to 
trap it on round trips, I'd also trap legitimate prolific users. And 
since you'd have to do some serious analysis of the majordomo logs to 
find it, one can only wonder how much bandwidth it ate before it died. 
At the time, my site would have killed it at 100 megs as a maximum 
message size. I now run a amximum message size much smaller... Just in 

>  In other words, you could make a rule something like:
>   Any given user cannot post more than 10 messages in a 24 hour period.
And I'd be constantly being blocked from any number of mailing lists, 
including, at times, this one.

That's the problem iwth this kind of "fix". you'll end up with false 
positives, and it doesn't fix the problem. It simply makes it less 
annoying; and it's arguable how much less...

Chuq Von Rospach, Internet Gnome <http://www.chuqui.com>
[<chuqui at plaidworks.com> = <me at chuqui.com> = <chuq at apple.com>]
Yes, yes, I've finally finished my home page. Lucky you.

Yes, I am an agent of Satan, but my duties
are largely ceremonial.

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